Milo g



(No Model.)

M. G. KELLOGG.

MULTIPLE SWITGHBOARD.

No. 592,318. Patented Oct. 26,1897.

Fig.1?

Line .714). 2.

wwxooeo UNTTED STATES PATENT OFFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SlVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOAR D.

SPECIFICATION forming part of Letters Patent No. 592,318, dated October 26, 1897.

Application filed November 29, 1889- Serial No. 332,021. (No model.)

To (all whom 2325 may concern.-

Be it known that I, MILO G. KELLOGG, of Chicag0,Illin0is,temporarilyresiding atStuttgart,in the Empire of German y,have invented certain new and useful Improvements in Multi ple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to single-circuit telephone-lines; and it consists in a system of switching and testing such lines to determine whether they are in use.

In the accompanying drawings, illustrating my im entiomFigures 1 and 1 are front views of sections of two multiple switchboards to which the same lines are connected. Fig. 2 is a diagram illustrating the main-line switchboards, apparatus, and connections necessary to illustrate my invention. Fig. 3 is a diagram of an operators cord system to be used in connection with said system. Fig. 4 is a diagram of a subscribers-station apparatus necessary to illustrate my invention.

In the figures like parts and apparatus are represented by the same letters and numerals of reference.

G is a ground connection.

In Fig. 2, A is a sectional view of the switchboard shown in Fig. 1*, and A is a sectional view of the board shown in Fig. 1., each as indicated by the line (Z c.

There are as many boards in the exchange as are necessary to answer the calls and make the connections. On each board is a springjack or similar switch for each line. Each switch has a contact-spring which normally bears on an insulated contact-point and has a contact-piece insulated from the rest, (except by the circuit connections,) and is adapted to receive a switch-plug, and when the plug is inserted to disconnect the spring from the contact-point and form connection between the spring and the contact-point of the plug.

In Fig. 2, g g represent-the springs of the different switches, h h the contact-points on which the springs normally bear, and jj the insulated contact-pieces of the switches. H are the switchholes. a b are the rubber strips on which the switch parts are mounted, as

shown, and through the fronts of which are the switch-holes Z I. These holes are adapted to receive the switch-plugs shown in Fig. 3 and marked D D, and when a plug is insert-ed into a switch it operates it as above described. The contact-pieces jj should be so placed that a test-plug or contact-point may be readily applied to them. Their function in this system is to form test-pieces or test contact-points for their lines, and they may be placed as shown, or in any convenient p0sition on their respective boards.

The connection of each line to the switchboards is as follows and as shown. A line normally grounded at the central office passes successively through the pairs of contactpoints of its switches on the boards, passing in each case to the spring first. It then passes through its line-annuuciator to ground. A suitable resistance-coil may also be placed in this ground connection, if desired, or a resistance-coil may be substituted for the resistance of the annunciator.

w is an annunciator, and a: is a resistanceooil. The contact-pieces j j of the line are connected to the line, the connection being be tween the switches and the resistance in the ground connection, whether annunciator or coil. In lines that are normally open to the ground at the central oflice the ground connection maybe leftoff and the line, after passing through the pairs of contact-points, as above indicated,is connected to contact-pieces jj of its switches. Independent calling-circuits are generally used for such lines, as in the Law system. Line No. 1, as marked, shows the connection of a line normally grounded and Line No. 2 of one normally open at the central office.

Fig. 3 shows an operators cord system with one pair of cords and their plugs, switchannunciator, key, and operators telephone and battery.

The plugs D D are constructed substantially as shown, on 111. being the rubber insulations and not their contact-pieces, and they should be inserted into the switches in such a position that the contact-piece of the plug is in connection with the switclrspring and is not in connection with the switch contactpiece 7'.

0 is a metal strip on which the bases of the plugs normally rest and which connects then the contact-pieces of the plugs with the ground.

y is the looping-in switch of the pair of cords.

o is the clearing-out annunciator, and 7c is the test-key.

t is the operators telephone, and B her calling and testing battery. The circuits are as shown.

The method of connecting other pairs of cords with their accompanying switches,keys, and apparatus to the telephone and battery will be apparent to those skilled in the art.

The method of operating the system in connection with the switchboards will be apparent to those skilled in the art. On account of the testing system, which will hereinafter be' explained, the operator in testing a line should use the plug marked \D, and consequently should preferably use the plug D in answering a call. Each operator has one cord system, with as many pairs of cords as she may need, and the parts are conveniently mounted and arranged at her board to operate the system.

In the subscribers station apparatus shown in Fig. 4, lis the calling-generator; 2, the signal-bell; 8, the subscribers telephone, and 4 the telephone-switch. The contact points and circuits are as shown, or otherwise arranged, so as to'sulostantially perform the operations hereinafter described. The signal-bell shown has an automatic electric-circuit breaker which makes and breaks the circuit when it is directly in the circuit of the line and a suitable current is sent over the line. Other devices for varying the current may be employed, some of which are hereinafter mentioned. When the subscribers telephone is on its switch, the circuitbreaker is in the direct circuit of the line and will respond to the current which may be sent over it.' When the telephone is off from theswitch, the circuit-breaker is shunted by a wire or small resistance, so that it will not respond to any current sent over the line.

The condition of the line is thereby changed when. the telephone is off from its switch from what it is when the telephone is on the switch, and this change of condition operates to determine the test, as will be apparent.

The system of testing is as follows: An operator on testing places the contact-piece or contact-point D of a pair of plugs on the contact piece or point j of the line to be tested and presses on the test-key 7c. The circuit connections through the switch Y are such that in order to include the test-telephone t the plug D must be used, and when a test is made the other-plug D of the pair should be removed from the ground-plate 0, and said plug will be generally in the switch of the line that has just called. Otherwise the test-.

battery would be short-circuited to earth through the ground-plate 0. If the line-is on the line.

not switched at any board, a complete circuit is established through her telephone and battery and the line, and if the subscribers telephone is on his switch the automatic cir cuit-breaker will be in the circuit and will operate -to make and break the circuit and the operator will hear the make and break and will know that the line is free. If, however, when she makes the test the line is switched at some other board, this circuit is open at the pair of contacts of the switch used and the instrument will not respond. If, again, the line is not switched at the central office, but the subscribers telephone is off its switch for use, the operators telephone will not respond to a make and break. WVhen an operator tests and gets no test response, she knows that either the line is switched for use at the central oifice or that the subscribers telephone is switched for use and that the line is thereby busy, and she will not connect it with another line. It will be observed that when a test is made, as indicated, of a line grounded at the central office part of the current will seek the ground through the resistance-coil and the annunciator and resistance of that part of the line which is in the circuit between the test-piece used and the ground. The proportion of current passing through this channel and that which passes over the line will depend on the comparativeresistances of the two circuits. A considerable resistance may, if desired, be placed in this ground-circuit at the office and thereby cause a large proportion of the current to go to line. The battery should be such as to operate the automatic circuitbreaker when it is connected in the test-circuit, as indicated. When a test is made and a line is switched, the operator will hear a click on making the test and on interrupting the connection. This, however, will be quite different from the continual make and break of a circuit-breaker and will not confuse her.

The automatic circuit-breaker or bell 2 at the subscribers station is illustrative or representative of a class of apparatus which gives a defined-indication on the test receiving instrument, or, in other words, an apparatus which produces a variable condition of the circuit or the electrical condition on the line; but my invention is in no sense limited to the particular type of such apparatus shown.

In the claims I have used the term current-varying device, intending to include thereby various kinds of devices or apparatus for varying the current or electrical condition Obviously any electrician may vary such apparatus, and as instances of obvious variations I refer to the following constructions which might be adopted:

First. A bell may be employed in which the contact points alternately shunt the bellmagnet when on closed circuit with the battery, thus alternately increasing and decreasing the resistance of the circuit.

Second. I may employ a constantly-operat ing rheotome actuated by a clock-movement or otherwise, with which there might be used a signal-bell that would respond to the makes and breaks of the rheotome.

Third. A resistance-coil and a constantlyoperating rheotome arrangedin multiple cii cuit might be used,the rheotome alternately short-circuiting the coiland thereby increasing and decreasing the resistance of the circuit. \Vith this arrangement a calling-bell could be employed that would respond to the increase and decrease of resistance.

Obviously any of these apparatus may be used in operating my invention, because the invention relates to a general organization or system and not to the details of the particular apparatus that may be employed at the subscribers station.

In multip1e-switchboard systems an operator to whom certain lines are assigned to answer frequently receives several calls at practically the same moment, and it may require some time before she can switch to a certain line and answer its call. In systems in which the test depends only on the switchin g of the line at some other board another op erator may in the meantime test the line, and finding it to test free may switch it to another line and cause annoyance and confusion to the subscriber; In my system this trouble is obviated, because as soon as the subscriber takes his telephone from its switch the line will test busy, whether or not it is switched at the central oifice. Again, in systems of testing which depend only on the subscribers telephone being on or oif its switch confusion frequently occurs from the fact that a subscriber places his telephone on its switch when he is .through conversation without sending in a clearing-out signal and his line tests free and is connected to when it is already switched at the central office with some other line. Lines in this condition are technically called tied up. In my system, again, this trouble is obviated,hecause the line will test busy until it is disconnected at the central office, whether or not the subscribers telephone is on its switch. The system therefore combines the advantages and obviates the disadvantages of the two general systems of testing outlined above.

I claim as my invention and desire to secure by Letters Patent 1. Atest-circuit for a subscribers line, containing an automatic circuit-breaker in the circuit at the subscribers station when his telephone is not switched for use but not otherwise, and at the central office a pair of contact-points open when the line is switched at its board but not otherwise, a pair of contactpoints normally open but closed by the operator on testing, and a test receiving instrument and battery, substantially'as set forth.

2. A test-circuit for a subscribers line, containing at the central ofiice a pair of contactpoints open when the line is switched at its.

board but not otherwise, a pair of contactpoints normally open but closed by the operator on testing, a test receiving instrument and battery, and a current-varying device at the subscribers station normally in said testcireuit but switched from it when the sub scribers telephone is switched for use, substantially as set forth.

A test-circuit for a subscribers line, con taining an automatic circuit-breaker at the subscribers station when his telephone is not switched for use but not otherwise, and at the central office a series of pairs of contact points normally closed, one pair on each of several multiple switchboards and each pair open when the line is switched at its board, a pair of contact-points normally open but closed by the operator on testing, and a test receiving instrument and battery, substantially as set forth.

I. A test-circuit for a subscribers line, containing at the central oifice a series of pairs of contact-points normally closed, one pair on each of several multiple switchboards and each pair open when the line is switched at its board, a pair of contact-points normally open but closed by the operator on testing, a test receiving instrument and battery, and a current varying device at the subscribers station normally in said test-circuit but switched from it when the subscribers telephone is switched for use, substantially as set forth.

5. A test-circuit fora subscribers line, containing at the subscribers station an automatic circuit-breaker in circuit when his telephone is not switched for use but not otherwise, and a pair of contact-points normally closed but open when the line is switched for use, a series of branch or derived circuits to said test-circuit, each containing a test receiving instrument and a pair of contact-points normally open but closed by the operator on testing, and a test-battery,substantially as set forth.

6. A test-circuit for a subscribers line, containin g at the central office a pair of contactpoints normally closed but open when the line is switched for use at its board, a branch or derived circuit to said test-circuit,containing a test receiving instrument and a pair of contact points normally open but closed by the operator on testing, and a testbattery, an instrument at the subscribers station which gives a defined indication on said test receiving instrument when closed with it and the battery and which is normally in said test-circuit but switched from it when the subscribers telephone is switched for use,

each pair open when the line is switched at tact-piece, said line passing through said conits board, a series of branch or derived circuits to said test-circuit, one for each of said boards and each containing a test receiving instrument, a battery, and a pair of contact points normally open but closed by an operator on testing, substantially as set forth.

8. A test-circuit for a subscribers line containing at the central office, a series of pairs of contact-points normally closed, one pair on each of several boards, and each pair open when the line is switched at its board, and a v series of branch or derived circuits to said erwise, a switch at the central ofiice having a pair of contact-points normally in contact, butseparated by the insertion of a switchplug, and a test contact-piece insulated from the rest, (except by the circuit connections,) said line passing through said pair of contactpoints and thence to said test contact-piece, in combination with a test receiving instrument grounded on one side and connected on its other side to a test plug or device, adapted, at the will of the operator to be brought into connection with said test contact-piece and a battery in the test-circuit, substantially as set forth.

\ 10. In a telephone-exchange system, a subscribers line normally grounded at the outer end and containing at the subscribers station an automatic circuit-breaker when the subscribers telephone is not switched for use, but not otherwise, and at thecentral office a switch containing a pair of contact-points normally in contact but separated by a switchplug on its insertion, a test contact-piece insulated from the rest (except by the circuit connections) and a resistance, said line passing through said pair of contact-points and thence through said resistance to ground, and said test contact-piece being connected to the line-circuit between the pair of contact-points and the resistance, in combination with atestwire containing a test receiving instrument and battery grounded at one end and connected at its other end to a test plug or device adapted, at the will of the operator, to be brought into connection with said test contact-piece, substantially as set forth.

1'1. In a telephone-exchange system,,asubscribers line grounded at its outer end, and at the central office, a switch containing a pair of contact-points, and an insulated test contact-points and thence being connected to said test contact-piece and said contact-points being normally in contact but opened by a switch-plug on its insertion, in combination with a test receiving instrument grounded at one sideand connected at its other side to a switch plug or device adapted, at the will of the operator, to be brought into connection with said test contact-piece, a battery in the test-circuit, and a current-varying device at the subscribers station normally in circuit with said line but switched from circuit when the subscribers telephone is switched for use, substantially as set forth.

12. In a telephone-exchange system, a sub-.

scribers line grounded at its outer end and.

of contact-points and thence through said resistance to ground and said test contact-piece being connected to its circuit between the pair of contact-points and the resistance, in combination with a test receiving instrument grounded on one side and connected on its other side to a test plug or device adapted, at the will of the operator, to be broughtinto connection with said test contact-piece, a battery in the circuit between the plug and the ground, and a current-varyin g device at the subscribers station normally in the circuit of the line but switched from the circuit when the subscribers telephone is switched for use, substantially as set forth.

13. In a telephone-exchange system, multiple switchboards, single-circuit lines connected to the same, each line being grounded at its outer end and having at its subscribers station an automatic circuit-breaker, and a switch with contact-points to switch the circuit-breaker into the circuit of the line when the subscribers telephone is not switched for use and to switch it from the circuit of the line when the telephone is switched for use, in combination with test contact-pieces one for each line on each board and normally connectedto the line, switches with contactpoints to disconnect any line from its test contact-pieces when it is switched for use, test telephone is not switched for use and to switch nect any line from its test contact-pieces when it is switched for use, resistance-coils, each grounded on one side and connected to the circuit of a line between the contact-points of its switches and its test contact-pieces, and test wires or circuits, one for each board, each containing it test receiving instrument and battery and grounded at one end and connected on its other end to a test plug ordevice adapted, at the will of an operator, to be brought into connection with any test contact-piece at her board, substantially as set forth.

In witness whereof I hereunto subscribe my name this 18th day of October, 1889.

MILO G. KELLO GG.

Vitnesses:

FRANCES D. KELLOGG, MARGARETHA RIEHL. 

